Door assemblies and the chain hoists used therewith are very well known in the art. For example, U.S. Pat. No. 6,712,116 B2 granted on Mar. 30, 2004, to the Applicant/Assignee of the present application (Canimex Inc.), and naming BEAUDOIN et al. as the inventors, relates to a drive mechanism for use with an overhead shaft of a sectional door, the content of this patent being incorporated herein by reference.
Also known to the Applicant are the following US patents and patent applications which describe various chain hoists and the like: U.S. Pat. Nos. 2,704,201; 2,773,668; 3,596,879; 4,399,908; 4,560,046; 4,792,323; 5,125,629; 5,927,690; 6,381,903 B1; 6,450,482 B1; 7,048,029 B2; 2004/0182528 A1; 2004/0211951 A1; and 2005/0043132 A1.
It is also known in the art that the rapid downfall of an inappropriately counterbalanced door assembly can sometimes result in the excessive rotation of the main shaft which is intended to operatively sustain torsional springs of the counterbalancing system of the door assembly. A pocket wheel is generally operatively fixed to said main shaft and a chain is operatively suspended about said pocket wheel. As is known, the operating of this chain enables the manual raising and lowering of the door assembly. When the door descends very quickly, the chain turns, looses its tension and may be drawn outside the pockets of the chain pulley given the centrifugal force created by the rotation of the shaft. In some cases even, although very unlikely, the chain may completely come off from the chain pulley and hit against an inside portion of the chain hoist when the latter comprises a casing that contains its components. Although very unlikely also, the chain may, in very exceptional cases, become “locked” (or “jammed”) in the chain hoist. This creates an important pressure on the internal components of the chain hoist which suddenly must retain the weight of the door, which is disadvantageous, for obvious reasons known in the art. Therefore, there is a substantial need to come up with an improved chain hoist and/or component to be used therewith which would be able to overcome the aforementioned prior art problem.
It is also known in the art that certain chains used in the industry of the garage door can, although very unlikely, in very exceptional cases, result in the formation of unwanted knots which may undesirably “lock” (or “jam”) the chain hoist, which is disadvantageous, for obvious reasons known in the art. Therefore, there is also a substantial need to come up with an improved chain hoist and/or component to be used therewith, which would overcome the aforementioned prior art problem.
It is also known in the art that, as a result of the above-discussed, and in some circumstances, conventional chain hoists tend to be quite noisy when internal components thereof and corresponding chain cooperate adversely with each other, which is also disadvantageous. Indeed, the faster a given chain turns about a chain pulley, the greater the risk of provoking resulting vibrations in the corresponding internal components of the chain hoist. Furthermore, noise is very often amplified by the resonance of the casing (typically, a metallic casing) created by a conventional closed chain hoist, which is also undesirable.
Hence, in light of the aforementioned, there is a need for an improved device, which by virtue of its design and components, would be able to overcome some of the above-discussed prior art problems.